1. Technical Field of the Invention
The present invention relates to a mask, a substrate with a light reflective film, a method for manufacturing a light reflective film, an optical display device, and an electronic apparatus, and more specifically, it relates to a mask for manufacturing a substrate with a light reflective film generating few interference fringes, a substrate with a light reflective film formed by using the mask, a method for manufacturing a light reflective film, an optical display device having a light reflective film on which hardly any interference fringes are generated, and an electronic apparatus having a light reflective film on which hardly any interference fringes are generated.
2. Related Art
As widely known, liquid crystal display devices are widely used as display devices in various electronic apparatuses because of their ability to reduce thickness and power consumption. Such liquid crystal display devices normally have a configuration in which a liquid crystal is injected between a pair of glass substrates and the peripheral edges of the substrates are sealed by a sealant. An electronic apparatus having such a liquid crystal display device therein adopts a configuration in which a protective plate is provided on the viewing side of the liquid crystal display device, that is, the side a viewer observes the display thereon, in order to protect the liquid crystal display device against external impacts. The protective plate is a plate-shaped member which is normally made of a material having light transmittance characteristics, for example, transparent plastic, etc.
However, in such protective plate, it is difficult to make its surface facing the liquid crystal display device completely smooth, and fine concave portions or convex portions exist on the surface in many cases. Therefore, in the case of providing such a protective plate on the liquid crystal display device, there is a problem that the display quality is greatly deteriorated due to the fine concave portions or convex portions on the surface.
One reason for the deterioration of the display quality is that the gap between the substrate at the viewing side and the protective plate in the liquid crystal display device is uneven due to the concavities or convexities existing on the surface of the protective plate. That is, corresponding to the unevenness of the gap, interference occurs when light coming from the liquid crystal display device passes through the protective plate and as a result, interference fringes are generated. It is presumed that the display quality is deteriorated because the generated interference fringes and the display images are mixed.
A reflective liquid crystal display device 400 as shown in FIG. 25 is disclosed in Japanese Unexamined Patent Application Publication No. 6-27481; a transflective type liquid crystal display device 500 as shown in FIG. 26 is disclosed in Japanese Unexamined Patent Application Publication No. 11-281972. In the respective devices, a plurality of concave or convex structures 404a, 404b (504a, 504b) having different heights from each other are provided to decrease the occurrence of interference fringes, and a high-molecular resin film 405 (505) is formed thereon, and a continuous wave-shaped reflective electrode 409 (509) is formed thereon.
In addition, a manufacturing process of a liquid crystal display device having such a reflective electrode is illustrated on FIG. 27, for example. First, as shown in FIG. 27(a), a photoresist film 602 is formed on the overall surface of a glass substrate 600, and then, as shown in FIG. 27(b), the photoresist film 602 is exposed through a pattern 604 comprising a plurality of circles of different diameters. Then, as shown in FIG. 27(c), it is developed, and a plurality of concave or convex portions 606a, 606b, each having different height and angle, are provided. Then, by heating the concave or convex portions and softening the angled portion of the concave or convex portions as shown in FIG. 27(d), angle-removed concave or convex portions 608a, 608b are formed. As shown in FIG. 27(e), the space 610 between the concave or convex structures is filled with a predetermined amount of high-molecular resin 620 to make a continuous layer having the wave-shaped surface. In addition, a wave-shaped reflective electrode 624 is formed on the high-molecular resin film 620 by using a stacking method such as a sputtering method.
The reflective liquid crystal display device or transflective liquid crystal display disclosed in Japanese Unexamined Patent Application Publication No. 6-27481, employs a mask pattern on which a plurality of circles of different diameters, are aligned uniformly or non-uniformly in part, to provide a structure having a plurality of concavities or convexities of different heights by using ultraviolet exposure and development. However, it is difficult to adjust the height precisely to effectively prevent the light interference because of the unevenness of the coating thickness, or the like. In addition, since a reflective electrode is formed on the structure having the plurality of concaves or convexes of different heights, there often occurs a breaking of wire or short circuit, too. In addition, the disclosed method for manufacturing a light reflective film involves many processing steps and management items to be processed, which results in many problems in the manufacture.
Therefore, according to the light reflective film disclosed in Japanese Unexamined Patent Application Publication No. 6-27481, it is not only difficult to prevent the occurrence of interference fringes effectively, but also difficult to manufacture such light reflective film stably and effectively.
Thus, there have been proposed methods for manufacturing the above-described reflective-type liquid crystal display device or the above-described transflective type liquid crystal display device using a mask in which light transmissive or non-transmissive portions are randomly arranged. Although the above-proposed methods reduce the occurrence of the interference fringe, a new problem has been found that stains of various shapes are seen on a screen, thereby causing remarkable deterioration of display quality.
The present inventors have extensively studied the above described problems and found that a light reflective film which generates few interference fringes while suppressing the occurrence of various-shaped stains when incorporated into a liquid crystal display device can be achieved by providing a plurality of concave portions or convex portions on a base at random and in a specific arrangement.
Therefore, it is an object of the present invention to provide a mask used for manufacturing a substrate with a light reflective film with reduced occurrence of the interference fringe, a substrate with a light reflective film obtained using the mask, a method for manufacturing the light reflective film, a liquid crystal display provided with the light reflective film, and an electronic apparatus comprising the light reflective film.